CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
J Chem Phys. 2012 Nov 21;137(19):195101. doi: 10.1063/1.4766319.
Ab initio constrained molecular dynamics and metadynamics were employed to investigate the mechanism of proton transfer in guanine-cytosine (GC) and adenine-thymine (AT) base pairs in the gas phase at room temperature. It is shown that double proton transfer (DPT) in the GC base pair is a concerted and asynchronous mechanism, and three pathways with a similar free energy barrier start from the canonical GC and end up in its "rare" imino-enol tautomer. The activation energy for the route that the DPT starts from the hydrogen atom movement in the O6(G)-N4(C) bridge is approximately 1.0 kcal/mol higher than that which starts in the N1(G)-N3(C) bridge. For the AT base pair, a stable intermediate state is identified in the two-dimensional free energy surface of the DPT event. We found that the movement of the hydrogen atom in the N1(A)-N3(T) bridge occurs before the movement of the hydrogen atom in the N6(A)-O4(T) bridge. Thus, it is demonstrated that the DPT in AT base pairs is a stepwise and an asynchronous mechanism.
采用从头算约束分子动力学和元动力学方法研究了室温下气相中鸟嘌呤-胞嘧啶（GC）和腺嘌呤-胸腺嘧啶（AT）碱基对中质子转移的机制。结果表明，GC 碱基对中的双质子转移（DPT）是协同的和异步的机制，有三个具有相似自由能势垒的途径从规范的 GC 开始，并最终到达其“罕见”的亚氨基-烯醇互变异构体。DPT 从 O6(G)-N4(C)桥中氢原子运动开始的途径的活化能比从 N1(G)-N3(C)桥中氢原子运动开始的途径的活化能约高 1.0 kcal/mol。对于 AT 碱基对，在 DPT 事件的二维自由能表面上确定了一个稳定的中间状态。我们发现，N1(A)-N3(T)桥中氢原子的运动先于 N6(A)-O4(T)桥中氢原子的运动。因此，证明了 AT 碱基对中的 DPT 是逐步的和异步的机制。
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